Sounds like he was kind of put on the defensive.
I'm willing to bet that the possibility of not just foam insulation coming off, but ice along with it is a possibility the NASA engineers could have easily overlooked in their analysis.
Common sense tells us that damage to left wing area is the cause of the left wing problems seen by ground control prior to the shuttle break-up.
My bet is NASA engineers already believe they screwed up.
It's the design that's screwed up.